Piston for internal combustion engines



PISTON FOR INTERNAL CMBUSTIONENAGINES May 19, 1942 w. L. scHoENGAR-rn 2,283,651

Y Y PISTQN FOR INTERNAL COMBUSTIONLENGINES I Filed" July 2o, 1940 Y s .shem.-=,shee-t z,

-May 179. 1942- w.L. scHoENGAR-m 2,283,651

PISTON FOR INTERNAL COMBUSTIONENGINES I Filed July 2o, 1940V l s sheets-sheet s Patented ay 19, 12

FISTON FR INTERNAL COMBUSTO ENGINES Walter L. Schoengarth, Ironwood, Mich., assignor to Benjamin G. Harmon, Chicago, lill.

Application July 20, 1940, Serial No. 346,529

9 Claims. (Cl. 309-11) The present invention relates to pistons, and more particularly to pistons for internal combustion engines. It has for its principal object the provision of a novel means for controlling the skirt diameter of the piston so as to maintain proper clearance with the cylinder for all temperatures of the engine. It is well-known that, particularly in the use of light weight metvals such as aluminum for pistons, the slnrt portion of the 'piston expands so rapidly with respect to the expansion of the cylinder that binding or seizing results at high temperatures and tooV much clearance exists at low temperatures. Objections to too much clearance such as piston slap and oil pumping are well-known in this art.

It has heretofore been proposed to split the aluminum skirt portion of the piston and to close it by various means such, for example, 'as the wedge device shown in :my prior Patentl #2,100,203. In' this case, the wedge device is actuated by a metal responsive to temperature changes, thereby controlling the skirt diameter. Various other 'devices depending upon dinerential expansions have been tried with more or less success. The present invention, however, distinguishes from these prior art devices in that it utilizes a new control means whereby the exfil skirt, and the stem of the Y is fastened to the piston head. I nnd, however, that it is better to v provide means for utilizing the piston head expansion in conjunction with the longitudinal expansion of the connecting webs and of the skirt itself to control the skirt diameter.

The lfeatures and advantages of the present invention will appear more `fully'as the descrippension of the piston head, the longitudinal expension of the webs connecting the head and skirt and the longitudinal expansion of the skirt itself .are employed conjointly to control the skirt diameter.

The present invention, in its preferred embodiment, contemplates the provision of a piston head wherein a Y-shaped element of a metal having a coemcient of expansion yless than that of the head, has the tips of the Y anchored in the head with the fork of the Y spaced therefrom, and has its stem depending longitudinally of the skirt. IThe stem of the Y is anchored to the skirt in such a fashion that the split skirt can be expanded or contracted responsive to expansion or contraction of the various members of the combination due to temperature changes. In a certain modiiied form of the invention, it is possible to do away withthe Y construction and employ simply bars which eiect the same result because of their cross relation, each bar, of course, being anchored atone end in the head and at the other end in the skirt. A further modicaton is not dependent upon the expansion of the piston head but utilizes the Y principle in a reverse construction where the Y arms of the Y are themselves anchored to the the skirt portion i6 near the lower part thereof.

tionproceeds, reference being had to the accompanying drawings wherein a preferred form of the invention is shown. It is to be understood, however, that the drawings and description are illustrative only and 'are not to be taken as limiting the invention except insofar as it is limited by the claims.

In the drawings,

Fig. 1 isa cross sectional View in side elevation of my piston, the view being taken on a plane through the control means on the line l--I of F18. 3; v

Fig. 2 is a view on the line 2-2 of Fig. 1;

Flg. 3 is a cross sectional' view on the'line 3-3 of Fig. l;

Fig. -4 is a view similar to Fig. 2 but showing the piston skirt oppositely split and having two temperature responsive control means;

Fig. 5 is a modification having the control free end of the Y anchored in the piston head,'

and

` Fig. l0 is a modication adaptable to relatively large piston units.

Referring now to 'the drawings, and particularly to Figs. l-3 inclusive, I show a piston comprising a head portion l5 and a skirt portion it.

Said portions are constructed of aluminum alloy or some similar light weight metal or alloy having a relatively high coefficient of thermal expansion. The two portions are spaced from one another as shown at H and are joined and held in alignment by means of webs i8 which are cast integral with the head portion i5 and with oppositely disposed bosses I9 which receive the connecting rod pins are carried on the web meniber I8 within the skirt portion of the piston.

As will be understood, the web members I8 have a certain resiliency in order to maintain a direct alignment of the bosses despite the slight diameter changes of the skirt. The skirt portion I6 throughout its length is provided with a slot so that the diameter of the skirt portion may be expanded and contracted, as will presently appear. The head portion I5 is not split, and thus retains its circumferential outline except as it may expand or contract due to changes in the temperature thereof. The said head portion I5 isprovided with a plurality of circumferential recesses 2| to receive piston rings, not shown. As will be understood, the diameter of the head portion I5 is of sucha size, somewhat Vsmaller' than the skirt portion, as never to bind with the cylinder wall regardless of the temperature. '.I'he reason for this is that the expansible piston rings bear against the cylinder wall and prevent loss of compression due to escape of gas and also prevent the passage of oil, thereby eliminating the necessity of maintaining a close fit between the head and the cylinder.

For controlling the diameter of the skirt portion of the piston, I provide a Y member of material such as Invar or other alloysv or metals having a relatively low coeicient of thermal expansion as compared to the material in the piston proper. The Y member has arms which are anchored in the head at separated points 26, spaced on either side of the vertical plane of the slot 20. The fork 21 of the Y is spaced from the head and the stem 28 of the Y depends longitudinally within the skirt member parallel to the said slot and terminates near the midpoint of the skirt length, Arms 29 integral with the stem 28 constitute an inverted Y and have free ends 30 anchored in lugs 3l projecting from the inner wall of the skirt on opposite sides of the slot. As can be seen from the drawings, the above described control device is disposed within the piston across the side of the skirt containing the slot 20. i

In operation, as the temperature of the cylinder and contained piston approaches working temperature, expansion results in the piston head, thereby increasing the distance between points 26 therein. Although the arms 25 also expand in length, the increase is relatively smaller than that in the lhead due to the lower coeiilcient of thermal expansion of the Invar arms or arms of other alloys or metals as compared to aluminum. Such differential expansion tends to draw the stem 28 towards the head I5.v

Such increased temperatures also will cause a longitudinal expansion of the webs I8, thereby tending to increase the distance between the points 30 and the piston head. Illhese expansions cause the distance between points 30 to contract -under the iniiuence of the arms 29, thereby drawing together the skirt at the slot, which of course reduces the diameter of the skirt and compensates for the increase in skirt diameter due to thermal expansion of the skirt. Proper choice of the various elements will result in a heat responsive control of the skirt diameter of the piston so as to maintain proper clearance under any and all conditions of temperature.

A modified form of my invention appears in Fig. 4 wherein I provide two slots 20 in the skirt portion, oppositely disposed, and provide duplicate heat responsive means, above described, for controlling the skirt diameter.

Fig. 5 discloses a piston of the character de- Cil - and its lower tips anchored in the lugs 36. As

scribed in my preferred embodiment but which will be understood, operation of this embodiment depends solely on the longitudinal and circumferential expansion of the skirt portion to maintain a substantially constant skirt diameter regardless of temperature.

Fig. 6 discloses two slots in the piston skirt with a control means such as shown in Fig. 5 disposed across each. It will be noted that in cross section the wall of the skirt between the slots is crescent shaped, that is, thicker at points 31 and decreasing in thickness towards the slots 20. The purposeof this eccentricity is to maintain a perfect circle throughout the temperature range, such provision being necessary because of the relatively greater expansion in the thickened portion of the skirt as compared to that in the thinner portion, such greater expansion being required to compensate for the drawing together of the skirt at the slots. Furthermore, the thickened portions ofthe skirt offset the weight of the control means, thereby presenting a piston balanced as to weight.

A further modification is disclosed in Fig. '1 wherein I have provided two crossed bars 40, each having their opposite ends respectively anchored to the head and to lugs 4I on lthe skirt of the piston. It will be noted that the head portion of the piston is integral with the skirt and that lateral slots 42 are provided throughout substantially ,each half of the circumference of the piston at the junction of the head and skirt portions. Longitudinal slots 43 extend from the mid-points of the lateral slots 42 throughout the length of the skirt. As can be seen in Fig. 8, the cross bars 40 are provided on each side of the piston to regulate the skirt diameter by meansof expanding or contracting the width of the side slots 43. such control being proportional to the longitudinal expansion ofthe piston between the head and the lugs 4 I.

Fig. 9 discloses a further modification of my control means wherein the inverted Y is used. The stem 45 of the Y is anchored to the head and the tips of the Y arevanchored to lugs'46 projecting from the skirt. This device of course does not utilize the lateralexpansion of the piston head and is dependent upon the expansion of the skirt and the expansion of the web members .connecting the head and the skirt.

Fig. 10 discloses a modification adaptable for use in relatively large pistons. The control device is substantially the same as disclosed in my preferred form with the exception that a second set of arms 41 are provided intermediate of the ends of the member 28 and have their tips anchored in lugs 48 provided on the inner side of the skirt in the upper portion thereof.

From the above description it is believed that the features and advantages of my invention will be readily apparent to those skilled in this art. Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a piston having a head portion and a circumferentially expansible and contraotible having a. relatively lower thermal coefficient of @,Qediii expansion than said head and skirt portions, said sides or" the slot therein.

2. In a piston having a head portion and a cir cumierentially expansible and contractible split skirt portion, a skirt circumference control mem.- ber disposed within said piston, said memberhaving a relatively lower thermal coefcient of expansion than said head and skirt portion, said member comprising a central portion having di` verging arms extending from the ends thereof and anchored within the piston, at least some of which arms are anchored to said skirt portion on opposite sides oi the slot therein.

3. In a piston having a head portion and a circumierentially expansible'and contractible skirt portion, a skirt circumference control member, said member having a relatively lower thermal coeicient of expansion than said head and skirt portions, said member comprising va central portion disposed lengthwise within said piston and having diverging arms extending from the-endsV thereof, the upper of said diverging arms being head, skirt and web portions, said control member having a plurality of arms angularly disposed with respect to each other and anchored within said piston, at least some of which arms are anchored to said skirt portion on opposite -sides-oi said slot.

5. In a piston having a head p0rtion,'an aligned 1 skirt portion having a longitudinal slot therein spaced from said head portion and joined' thereto by web members, a skirt circumference control d. In a piston having a head portion, an aligned skirt portion having a longitudinal slot therein spaced from said head portion and joined thereto by web members, a skirt circumference control member disposed within said piston and across said slot, said control member having a relatively lower thermal coefficient oi expansion than said head, skirt and web portions, said control rnern`= ber comprising a central portion having diverging arms extending from the ends thereof and anchored within the piston; the 'upper of said di verging arms being anchored to said head pore'.

tion, and the lower of said arms being anchored to said skirt portion on opposite sides of said slot.

7. In a piston having a head portion, an aligned skirt portion having a longitudinal slot therein spaced from said head portion and joined thereto by web members, a skirt circumference control member disposed within said piston and across said slot, said control member having a relatively lower thermal coeicient of expansion than said head, skirt and web portions, said control membei' comprising a central portion lhaving diverging arms extending from the ends thereof 'and an chored within the piston, the upper of said diverglng arms being anchored to saidskirt portion rnear the top thereof and on opposite sides of said slot, the lower of said arms being anchored to the skirt portion near the bottom thereof and on opposite sides of said slot.

8. In apiston having a head portion, an aligned skirt portion having a longitudinal slot thereinv spaced from said head portion and joined thereto by web members, a skirt circumference control member disposed within said piston and across saiclslot,l said control member' having a relatively lower thermal coethcient of expansion than said head, skirt and web portions, said control member being an inverted Y having. its lower tips anchored to said skirt portion on opposite sides oi said slot, the upper end oi the stem of the member being anchored to said head.

9. In a piston having Va. head portionand a cir cumferentially expansible and contractible skirt portion provided with a slot therem, me to expand and contract said slot to change the s circumference, said means comprising a Y shaped strut -the stem of which extends lengthwise of the piston, and the tips oi which are anchored in theskirt on opposite sides oi said slot. 

